Speedwell Cavern

it consists of a horizontal lead miners' adit (a level passageway driven horizontally into the hillside) leading to the cavern itself, a limestone cave. The adit is permanently flooded, resulting in Speedwell Cavern's (locally unique) feature: after descending a long staircase, the visitor makes the journey into the cave by boat. Originally the guide propelled the boat by pushing against the walls with his hands, later the boat was legged through, and now it is powered by an electric motor.

At the end of the adit, the visitor alights from the boat and walks into the cave to see the fluorspar veins, the stalactites and stalagmites, and the so-called "Bottomless Pit". This pit is an extremely deep vertical shaft, now choked to within 20 metres (66 ft) of the surface by rock spoil dumped by miners. The original depth of the shaft has been estimated, from the amount of spoil placed in the shaft over the years, at around 150 metres (490 ft). Wikimedia Commons has media related to Speedwell Cavern.

A connection was discovered in 1999 between the Speedwell Cavern system and Titan, the largest natural shaft in the UK, which is 141.5 metres (464 ft) high.Wikipedia

Set at the foot of the spectacular Winnats Pass, high above the village of Castleton, Speedwell Cavern takes you on a fascinating boat journey through the abandoned workings of an eighteenth century lead mine.

Descend the 106 steps from the almost hidden cave entrance to the landing stage of an underground canal where you step on to your tour guides' boat. From here your guide takes you through the workings of a 200 year old lead mine. Picture in your mind what it must have been like to carve out these tunnels using only the most primitive tools as your guide recounts the story of the mine which opens into a network of natural caverns and underground rivers.At Halfway House the canal tunnel splits into two to allow oncoming boats to pass as you make your way 200 meters below the surface of the hill before entering a huge cathedral-like cavern containing the Bottomless Pit - a huge subterranean lake.At the Journey’s End visit the gift shop and take home something to remember the eerie splendour of your journey into the depths of Speedwell Cavern. A wide selection of gifts and mementos is available including jewellery made from the exclusive Blue John stone - the superb fluorspar mineral unique to the Peak District Caverns. Cavern craftsmen are often commissioned to make commemorative pieces from this world-famous stone such as a chalice made for Her Majesty the Queen on her Silver Jubilee.The Cavern is open daily (except Christmas Day) from 10am to 5pm (last tour leaves at 4pm) in summer, and from 10am to 4pm (last tour leaves at 3.00pm) in winter.